1. Field of the Invention
The invention relates to the air induction and exhaust discharge processes of piston driven internal combustion engines which operate on either the two-stroke principle or four-stroke principle. In particular, the invention provides a new and useful process application of the gas ejector system in a manner which is unique in the operation of piston driven internal combustion engines.
2. Description of Prior Art
In its conventional application to the control of process cycles of the piston driven internal combustion engine, the gas ejector system is mounted on a engine cylinder wall port which is situated at a point near the bottom-dead-center of piston travel. The ejector port is periodically brought into communication with the displacement volume of the engine cylinder by the reciprocating motion of the engine piston as it alternately covers and uncovers the engine cylinder port.
In the present invention a second gas ejector port is situated in the engine cylinder head and is brought into communication with the clearance volume above the engine piston by the opening and closing of a cam operated poppet valve.
McWhorter describes in his U.S. Pat. Nos. 4108119, 4248199 and 4312313 the component elements of the gas ejector and teaches its useful operation in the control of gas flow within the piston driven internal combustion engine when mounted at an engine cylinder port situated above the point of bottom dead center of piston travel. The benefits of the gas ejector are well established in McWhorter's U.S. Pats. and are not mentioned in this application.
In the design of most standard engine systems two poppet valves are employed in the engine cylinder head to control the unidirectional flow through their corresponding ports and are thus able to regulate the flow of air charge to the engine cylinder and flow of combustion gas from the engine cylinder. The newer high performance engines used in todays automobiles now contain as many as four such poppet valves per engine cylinder. This has been done primarily to improve volumetric efficiency and to permit the manufacturer to decrease the engine size without loss of power to weight ratio necessary for improved fuel economy, drivability and safe highway operation. However, increasing the number of poppet valve control elements in the engine cylinder head absorbs power from the engine system by the energy required in the compression of the additional heavy valve springs and by frictional losses in valve gearing, cam bearings, sliding action of cam lobes, and the linear reciprocating of valve stems within the valve guides. Coupled with these losses are the normal inertial losses required to accelerate the increased mass of the additional poppet valve components. It should also be noted that the opportunity for component failure is increased by the greater number of moving parts to be considered in the statistical population. The additional complication of poppet valve control elements also increases the engine manufacturing costs.
In the present invention the number of poppet control valve elements is halved thereby reducing the amount of energy required for valve operation. The smaller number of moving parts required in the invention reduces the statistical incidence of failures and reduces the repair and general servicing expense. The reduction in the number of closely machined poppet valve actuation components made possible by this invention also reduces the manufacturing cost. It should also be noted that by the operation of fewer valve components made possible by the unique engine process the noise is decreased.
Another unique feature of the invention is seen in its ability to provide convective cooling to the poppet valve and poppet valve seat surfaces by the flow of the induction air following the exhaust cycle. This is made possible by the use of the gas ejector circuits described in those U.S. Patents presented in the above Cross Reference. These gas ejector circuits permit the bidirectional flow within the poppet valve port without serious exhaust gas dilution during the air induction.
The conversion of the Otto cycle or Diesel cycle, from four-stroke to two-stroke operation or vice versa cannot be accomplished in todays engines without engine tear-down and mechanical refitting. In the present invention the conversion to either method of operation is automatically achieved while the engine is running. This is accomplished by gearing the engine camshaft to operate at the same number of revolutions per minute as the engine crankshaft. Therefore, for the purpose of discussion it may be assumed that the poppet valve is always closed when the piston is at the top dead center of its travel and is always open when the piston is at the bottom dead center of its travel. Those skilled in the art will immediately recognize that by operating the poppet valve in this manner causes it to move at twice the cycle frequency as that required in the four-stroke engine. This higher cycle frequency permits the automatic conversion from low speed four-stroke operation to high speed two-stroke operation by electronic timing circuits which sense the engine speed and pressure and automatically change the rate of spark ignition and fuel injection. Other engine parameters such as temperature or engine torque may be used to control the process with equal success.
At engine start-up, and at low engine speeds and high torque conditions, the engine is operated as a four-stroke system. At high engine speeds and low torque conditions the system converts to two-stroke operation for better fuel economy.